Hey

NCC is National Cadet corps which gives training's to  youngsters to become patriotic and disciplined citizens.  The Minimum age to join NCC  is 13 years and Maximum age is 26  years, as of now you are in your Bsc third year but you can not join NCC beacuse  the duration of NCC is 3  years  for the first two year of NCC training you will get B certificate and for next one year you will get C certificate. so, its hard to say but you cannot join NCC because it is your last year in college and you will not be able to continue the tenure of 3 years of NCC training , so unfortunately you cannot join NCC in third year of your college.

Good luck!